A metal sphere of radius 10 cm is given a charge of $12μC$. The force acting on unit area of its surface due to its own charge is

$5.157 × 10^2 N/m^2$

Let charge per unit area is $\sigma = \frac{Q}{4\pi R^2}$

Electric Field due to sphere near its surface$ E = \frac{\sigma}{2\epsilon_0}$

Force on its unit area $ F = \sigma \times E = \sigma \times \frac{\sigma}{2\epsilon_0}= \frac{\sigma^2}{2\epsilon_0} = 515.7 N/m^2$